Method and apparatus for die stacking

Abstract

An integrated circuit package is constructed by attaching lower dies to a substrate that has bond fingers deposited on its surface. One lower die and its associated bond fingers are located offset from the center of the substrate. The lower dies are electrically coupled to the substrate's bond fingers with lower bond wires. An upper die is stacked on at least one of the lower dies. The upper die is electrically coupled, with bond wires, to the lower die upon which it is mechanically coupled. Each of the lower dies may be coupled to the other lower die with bond wire bridges that span the lower bond wires. The upper die may be electrically coupled, with bond wire bridges, to any or all of the lower dies.

What is claimed is:  
     
       1. A method of constructing an integrated circuit apparatus comprising stacked dies, the method comprising: 
       generating a substrate including a plurality of bond fingers grouped in an offset location of the substrate, the offset location being offset relative to a center of the substrate;  
       coupling a first lower die to the substrate in the offset location, the first lower die having a plurality of periphery pads and a plurality of inner pads;  
       coupling a stacked die to the first lower die with the plurality of inner pads;  
       coupling the stacked die to the substrate such that the stacked die is coupled to a subset of the plurality of bond fingers in the offset location coupling the first lower die to the substrate includes electrically coupling the plurality of periphery pads to the plurality of bond fingers using lower die bond wires; and coupling a second lower die to the substrate, the second lower die being coupled to the first lower die with bond wires that bridge the lower bond wires.  
     
     
       2. The method of  claim 1 , wherein coupling the first lower die to the substrate includes mechanically coupling the first lower die to the substrate using epoxy. 
     
     
       3. The method of  claim 1 , further comprising coupling the stacked die to the second lower die with bond wires that bridge the lower bond wires used to couple the first or second lower dies to the substrate. 
     
     
       4. A method of constructing an integrated circuit apparatus comprising stacked dies, the method comprising: 
       generating a substrate including a plurality of bond fingers grouped in an offset location of the substrate, the offset location being offset relative to a center of the substrate;  
       coupling first and second lower dies to the substrate such that pads on the periphery of the first lower die are coupled to the plurality of bond fingers with a first set of lower bond wires, and pads on one edge of the second lower die are coupled to the plurality of bond fingers with a second set of lower bond wires; and  
       coupling a first stacked die directly to the first lower die with upper bond wires through inner pads on the first lower die.  
     
     
       5. The method of  claim 4 , wherein coupling the first and second lower dies comprises: 
       coupling the first lower die in the offset location such that it is surrounded by the plurality of bond fingers grouped in the offset location; and  
       coupling the second lower die laterally to the first lower die via bridge bond wires.  
     
     
       6. The method of  claim 4  further comprising electrically coupling the first stacked die to the second lower die with bridge bond wires such that the bridge bond wires span at least one set of the first and second sets of lower bond wires. 
     
     
       7. The method of  claim 4 , further comprising coupling the first stacked die to the substrate with bond wires. 
     
     
       8. The method of  claim 4 , further comprising coupling a second upper die to the first lower die. 
     
     
       9. The method of  claim 8 , further comprising generating the second lower die with a plurality of bond pads grouped in a predetermined area closest to the first lower die. 
     
     
       10. The method of  claim 8 , further comprising electrically coupling the second stacked die to the second lower die with bridge bond wires that span at least one of the first and second sets of lower bond wires. 
     
     
       11. The method of  claim 4 , further comprising: 
       coupling a third lower die to the substrate, the third lower die comprising a plurality of pads along a first side closest to the first lower die; and  
       electrically coupling the plurality of pads along the first side of the third lower die to the first lower die with bridge bond wires spanning the first set of lower bond wires.  
     
     
       12. A method of constructing an integrated circuit apparatus comprising stacked dies, the method comprising: 
       generating a substrate including a plurality of bond fingers located in an area surrounding a die area offset from a center of the substrate;  
       electrically coupling a first lower die to the substrate such that a first row of periphery pads on the first lower die are coupled to the plurality of bond fingers with lower bond wires, the first lower die additionally including a second row of periphery pads on at least one side and substantially adjacent to the first row of periphery pads;  
       electrically coupling a second lower die to the first lower die with bridge bond wires spanning the lower bond wires from a row of pads on the second lower die to the second row of periphery pads on the first lower die;  
       electrically coupling, with bond wires, first and second stacked dies to the first lower die; and  
       electrically coupling at least the first stacked die to a subset of the plurality of bond fingers with bond wires.  
     
     
       13. A method of constructing an integrated circuit apparatus comprising stacked dies, the method comprising: 
       generating a substrate including a plurality of bond fingers grouped in an offset location of the substrate, the offset location being offset relative to a center of the substrate but along a centerline of the substrate;  
       coupling a first lower die to the substrate in the offset location, the first lower die having a plurality of first row periphery pads, a plurality of inner pads, and a plurality of second row periphery pads along at least one side of the first lower die;  
       coupling a second lower die to the substrate in a position between one edge of the substrate and one edge of the first lower die, the second lower die including a plurality of bond pads grouped along one edge of the second lower die closest to the first lower die;  
       coupling the first lower die to the plurality of bond fingers with lower bond wires;  
       coupling the second lower die to a first subset of bond fingers of the plurality of bond fingers;  
       coupling a first stacked die to the first lower die, the first stacked die including a plurality of periphery pads, a first subset of which is coupled to the inner pads with bond wires, a second subset of the first stacked die periphery pads being coupled to a subset of the plurality of bond fingers;  
       coupling a second stacked die to the second lower die, the second stacked die including a plurality of bond pads grouped along one edge of the second stacked die; and  
       coupling the second stacked die to the first lower die with bridge bond wires that span the lower bond wires and couple the plurality of second stacked die bond pads to the plurality of second row periphery pads.